I really don't get it.The other weird thing is all the cars show up like clockwork right around 9:30pm (also not an ideal time to confront a number of dudes (albeit a lot smaller than me lol).

There would be many different  to do this but this made sense to avoid confrontation. 

Everybody saves face, no confrontation - but you called her bluff.  

When confronted, she stated that the dog was a service dog for her disabled son.

Never get in these confrontations with tenants.

Believe me when I tell you, the time and money you can lose over emotional tenant confrontations staggers the imagination.THE LANDLORD’S MIND – IT’S A TERRIBLE THING TO WASTEDoing business with tenants is what us landlords do.

That being said, if you're really that concerned and don't feel like having a confrontation you could always let him fill out an application and then deny him.

Actually the lease is with her husband and I don't see that it is my place to approach her directly sure I understand your point but I don't want to make the situation confrontational for a person who may have nothing to loose. 

I appreciate the boldness of confrontation in constructive mannerism.

Sometimes you have to confront these shady characters in person, whether at their place of business or home.